Question: Solve for $x$ and $y$ using substitution. ${-4x+2y = 8}$ ${y = -3x-1}$
Explanation: Since $y$ has already been solved for, substitute $-3x-1$ for $y$ in the first equation. ${-4x + 2}{(-3x-1)}{= 8}$ Simplify and solve for $x$ $-4x-6x - 2 = 8$ $-10x-2 = 8$ $-10x-2{+2} = 8{+2}$ $-10x = 10$ $\dfrac{-10x}{{-10}} = \dfrac{10}{{-10}}$ ${x = -1}$ Now that you know ${x = -1}$ , plug it back into $\thinspace {y = -3x-1}\thinspace$ to find $y$ ${y = -3}{(-1)}{ - 1}$ $y = 3 - 1$ $y = 2$ You can also plug ${x = -1}$ into $\thinspace {-4x+2y = 8}\thinspace$ and get the same answer for $y$ : ${-4}{(-1)}{ + 2y = 8}$ ${y = 2}$